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Ophthalmic Optical Instruments I

Ophthalmic Optical Instruments I. Telescopes and Microscopes. C. I. OPHTMALMOMETER, CHICAGO ILLINOIS ca 1899. TELESCOPES. f o. M = -. f e. Astronomical (Keplerian) Telescope. Image is Inverted. objective. eyepiece. F o. F e. f e. f o. Virtual image at 25 cm. D.

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Ophthalmic Optical Instruments I

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  1. Ophthalmic Optical Instruments I Telescopes and Microscopes C. I. OPHTMALMOMETER, CHICAGO ILLINOIS ca 1899

  2. TELESCOPES

  3. fo M = - fe Astronomical (Keplerian) Telescope Image is Inverted objective eyepiece Fo Fe fe fo Virtual image at 25 cm

  4. D Astronomical Telescope objective eyepiece Fe Fo fe fo Virtual image at infinity

  5. plus lens fp fp negative lens Galilean Telescope fp fp’s coincide final telescope parallel rays

  6. Viewing Through a Galilean Telescope parallel iImage rays object emmetropic eye UPRIGHT OBJECT APPEARS UPRIGHT D GTT 04

  7. MICROSCOPES

  8. ANGULAR MAGNIFICATION Apparent size of object depends on angle it subtends at eye.

  9. ANGULAR MAGNIFICATION On average, an object cannot be closer than 25 cm from the eye to be seen clearly. Average distance of most distinct vision

  10. cm (cm)

  11. BASIC MICROSCOPE magnifier real image magnification

  12. MICROSCOPE MAGNIFICATION 25 = M f 2 Im 25 Im = M = M X Ob Ob 1 f total

  13. OBJECTIVES n a Numerical Aperture (NA) Light gathering ability Resolution a NA = sin n EXAMPLE a = 14 D n = 1.00 (air) w.d. NA = 1.00 x sin(14 ) NA = 0.24

  14. OBJECTIVES N.A. Examples

  15. D EYEPIECES (OCULARS) Huygens Ramsden parallel rays from eyepiece Real image Real image converging rays from objective

  16. REAL MICROSCOPE

  17. EXPERIMENT 4 Basic Microscope iris diaphragm real image on card onion skin f Produce real image of onion skin on card. Mark distance of real image on base.

  18. EXPERIMENT 4--CONTINUED View real image with magnifier (“eyepiece”) real image plane f Adjust iris diaphragm. How does image change? 25 Im What is the total magnification? = M X Ob f total

  19. Slit-lamp Biomicroscope

  20. The slit-lamp biomicroscope begins with a microscope…. Eyepiece Objective Specimen

  21. ….turned on its side ….change specimen, objective & eyepiece Huygens eyepiece objective subject image plane …….fundamental slit-lamp biomicroscope

  22. Build in magnification change without changing working distance working distance fobj Galilean telescope to change mag no image in image plane

  23. D Build in magnification change without changing working distance working distance fobj Galilean telescope to change mag no image in image plane

  24. D …..add lens to form image in eyepiece image plane astronomical telescope

  25. 2 right-angle prisms 1800 image rotation displace image horizontally reduce length of telescope Porro* prism Porro -Abbe *Ignazio Porro. 1801 – 1875. Italian optical instrument maker

  26. D Slit-lamp with folded optical path

  27. D

  28. binocular slit-lamp viewing system

  29. Operating Microscope

  30. Operating microscope optics are very similar to those of the slit-lamp.

  31. binocular astronomical telescopes Change magnification without changing working distance magnification change: Galilean telescopes prism objective lens

  32. Useful in seeing corneal endothelial cells Endothelial cells posterior surfaces flat & adjacent to aqueous Difference in index of refraction gives specular reflection Specular Microscope specular == “mirror-like”

  33. D Specular Microscope halogen lamp condenser slit dipping cone lens M objective film or CCD Ramsden eyepiece

  34. endothelium { slit image specular reflections and stray light

  35. Typical image of endothelium from specular microscope

  36. Confocal Principle Red cell in thick sample imaged by lens Pinhole in image plane passes all light from blue cell Blue cell, nearer to surface, imaged at different point Pinhole blocks most of light from red cell Based on Webb, RH, Rep Prog Phys 59:427

  37. Confocal Principle Point source CONFOCAL with blue cell & pinhole selectively illuminates blue cell Confocal point source gives less light to red cell, and most is blocked by pinhole Beam splitter makes confocal microscope epitaxial Based on Webb, RH, Rep Prog Phys 59:427

  38. Confocal Optical Systems: Pinhole allows light from small volume in sample. Other stray light blocked. Confocal point source confines light to small volume in sample. Rejects stray light Allows Z-axis “sectioning”

  39. Confocal systems can improve imaging Standard specular microscope Confocal specular microscope

  40. Koester’s confocal microscope

  41. CCD camera M lamp M confocal slit slit rotating mirror Koester’s Confocal scanning microscope objective specimen

  42. Tandem Scanning Confocal Microscope Scanned (laser) Spot Confocal Microscope Scanned Slit Confocal Microscope Other Scanning Methods and Confocal Microscopes

  43. Uses Nipkow disk Paul Nipkow (1860 -1940) Studied with Helmholtz Invented disk in 1883 Used for telegraphing pictures Later used in 1st television r q Sets of holes in plate Holes on Archimedes spirals r = a + bq D Tandem Scanning Confocal Microscope

  44. Very light inefficient Petran Tandem Confocal Scanning Microscope

  45. TCSM for imaging cornea

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